This invention relates to a shifting apparatus for the transmission of a marine outboard drive unit and more particularly to an improved and simplified shifting arrangement.
As is well known, outboard drive units normally embody a forward/reverse transmission in their lower unit. The transmission normally comprises a pair of bevel gears that are rotatably journalled on the propeller shaft and which are driven in opposite directions by means of the engine. A clutching mechanism is provided for selectively clutching one of these gears to the propeller shaft to drive the propeller shaft in either a forward or neutral direction. Shifting is controlled by means of a control lever or rod that extends through the upper unit and drive shaft housing and which is operated so as to select the appropriate gear. The control rod normally operates a plunger that is supported internally of the propeller shaft for shifting the clutch element. Because of the fairly large number of parts employed and the relatively compact construction of such transmission and shifting units, installation, assembly and repair are complicated. Furthermore, the use of separate parts gives rise to a difficulty in insuring that the parts are all properly assembled.
It is, therefore, a principal object of this invention to provide an improved, simplified shifting arrangement for an outboard drive.
It is another object of this invention to provide a simplified shift controlling mechanism for an outboard drive.
The clutching elements employed for clutching the respective driven bevel gear to the propeller shaft normally is of the dog type. By employing such positive clutching elements, it is essential to insure that the shift from neutral to either forward or reverse drive is made quickly so as to avoid clashing of the engaging clutch elements. It has been proposed to provide a detent mechanism internally of the clutch actuator that will resist shifting movement until a predetermined force is applied. It has also been proposed to employ a long torsionally resilient shift rod that will wind up when the detent is loaded and suddenly released its stored resilient energy to snap the clutch elements into engagement. Although such an arrangement provides extremely good clutch operation, the addition of the detent into the clutch actuating mechanism, particularly when confined within the propeller shaft, can further complicate the construction and render both assembly and servicing difficult as aforenoted.
It is, therefore, a still further object of this invention to provide an improved and simplified shifting arrangement for the transmission of an outboard drive that provides for snap engagement of the clutching members.